Inhalation of cotton plant debris dispersed as dust produces byssinosis in workers making cotton thread and cloth. Our project aims to determine the chemical nature of the agent which recruits polymorphonuclear leukocytes into airway epithelia and lumens in both human subjects and experimentally exposed hamsters and guinea pigs. Chemical isolation and identification are being guided by a bioassay for chemotaxis of leukocytes in Boyden type chambers. An ethyl acetate extract of cotton dust or trash is purified on florisil and further separated by thin layer chromatography on silica gel plates. One fluorescent spot contains a leukocyte chemotactic agent and tests positive for coumarin but is unstable. Other spots do not attract leukocytes. This material which is chemotactic is also cytotoxic so doses must be carefully adjusted in the chambers. Batch purification is being done with gas-liquid chromatography after pre-purification on florisil. We plan to purify the agent by high pressure liquid chromatography, identify its molecular weight by mass spectrometer and continue monitoring activity by leukocyte chemotaxis.